We propose to conduct a broad field evaluation of the newly developed, simple, sensitive, specific, rapid latex test for the detection of Rocky Mountain spotted fever in collaboration with other state health departments where RMSF is endemic. The field evaluation will proceed in three stages. The collaborating laboratory will first acquire proficiency on the latex test and share its observations with the Albany laboratory. During the second stage unknown serum specimens will be sent to the collaborating laboratory to test inter- and intra-laboratory reproducibility. Stage three will begin with the 1980 RMSF season and will involve the splitting and simultaneous testing of all specimens received for RMSF testing by both Albany and collaborating laboratory. Result reports would be held by a third party and released (fall, 1980) after all testing has been completed. This third stage will help to evaluate the latex test in different laboratories under day to day conditions.